There is a difference between basing your business on commodity offerings (say, Linux vservers) where there is active competition, and basing your business on a

There is a difference between basing your business on commodity offerings (say, Linux vservers) where there is active competition, and basing your business on a walled garden of harder to replace services (say, Appengine, or S3, or Twitter or Facebook). Appengine is hard to replace, but there are some immature alternatives out there. Same for S3. If you rely on Twitter or Facebook, you are completely locked in. His point is, the more proprietary the stack you rely on, the more likely you are to get the thumbscrews when people start more aggressively monetizing - or the more likely you are to lose everything if the tech you are building on disappears or locks you out.